Spin packs for extruding component fibers are known. Such spin packs are of two general types: those which spin multicomponent filaments (more than one component within a single filament); and those which spin mixed filament yarn (more than one type of filament within a yarn). In this application, the term "multicomponent yarn" refers to both of these general types as well as combinations of the two. The term "active backhole" denotes backholes for spinneret orifices that are, or will be, actively extruding filaments.
Exemplary of spin packs for mixed filament yarn is U.S. Pat. No. 3,457,341 to Duncan et al., which discloses spinning mixed filament yarn by extruding two different polymer components through two different sized orifices of the same spinneret. This is done to control differential spinning characteristics of the individual polymers within established levels of operability.
Exemplary of spin packs for multicomponent filaments is U.S. Pat. No. 3,730,662 to Nunning. Nunning discloses a spin pack for spinning side-by-side or sheath/core filaments by distributing mutually separated polymer streams to each spinneret backhole. Each discrete stream enters each active backhole.
Known are spinnerets useful for spinning both multicomponent and "ordinary" (single-component) filaments by simple rotation of a distribution plate. Such a device is disclosed in U.S. Pat. No. 3,584,339 to Kamachi et al.
Also, known is an apparatus for preparing profiled multicomponent fibers from mutually separated polymer streams. Such an apparatus is described in commonly assigned PCT Application No. WO 89/02938. In that apparatus, mutually separated polymer streams are routed in a predetermined fashion to the backhole of each spinneret orifice.
Yet, all of the known spin packs are designed for spinning one or two predetermined and fixed multicomponent or mixed filaments. Especially valuable would be a spin pack which routes multiple mutually separated polymer streams to the proximity of the spinneret backhole and allows variable selection at the backhole of the polymer stream which issues through the spinneret orifice.
Such a spin pack would be useful in preparing uniformly spread components in mixed filament yarn, inter alia. U.S. Pat. No. 3,681,910 to Reese teaches a composite yarn of two discrete classes having a high degree of filament mixing. Yet, high filament mixing (or distribution) in yarns composed of more than two discrete classes is unknown in the art.
Also useful would be a yarn in which a high degree of filament mixing is present in one area of the yarn and components in other areas of the yarn, one or more filament types are concentrated. Such an arrangement of mixed and non-mixed areas result in a heather yarn with a pleasing color highlight effect. Such a yarn is also not known.